Process for the production of ink transfer media



United States Patent 3,260,779 PROCESS FOR THE PRODUCTION OF INKTRANSFER MEDIA Albert E. Tarbox, Bridgewater Township, Somerset County,N.J., assignor to Union Carbide Corporation, a corporation of New YorkNo Drawing. Original application Nov. 30, 1961, Ser. No. 156,165.Divided and this application Aug. 5, 1963, Ser. No. 305,571

11 Claims. (Cl. 264-293) This application is a division of applicationSerial Number 156,165, filed November 30, 1961.

This invention relates to ink transfer media and to a process for theproduction thereof. More particularly, this invention relates to aprocess for the production of ink transfer media, such as printingplates, which have excellent ink transfer characteristics, defect-freesurfaces and excellent resistivity to the swelling action of practicallyall of the common ink solvents.

Printing plates having excellent ink transfer characteristics,defect-free surfaces and resistance to the swelling action of inksolvents, are mandatory in printing operations which employ such inktransfer media, in order to produce printed surfaces whereon the printis sharp, clear and legible. In printing operations such as letter-pressprinting, dry-offset printing and fiexographic printing, printing platesreceive ink and transfer the ink received to another surface. As anillustration, in both letterpress printing and in fiexographic printing,the printing plate receives ink from ink rollers and then transfers theink to the surface to be printed on, reproducing thereon a mirror imageof its, the printing plates surface. If the printing plate does not havea defect-free surface and excellent resistivity to the swelling actionof the ink solvent, the printed surface will be smeared and thereproduction appearing thereon will be imperfect due to the irregularsurface of the printing plate. In those instances wherein the printingplate does not have excellent ink transfer characteristics, the printedsurface will also be unsatisfactory due to a poor distribution of inkfrom the printing plate to the surface to be printed on.

In the past, printing plates, especially those used in flexographicprinting and in some letter-press printing, have been made of natural orsynthetic rubber. Such printing plates are flexible, resilient andexhibit good wear resistance. The use of rubber printing plates has beenlimited, however, since they have relatively poor resistance to theswelling action of a large number of the common ink solvents. Commonlyused ink solvents such 'as methyl ethyl ketone, acetone, isophorone,cyclohexane and the like cause rubber printing plates to swell to anundesirable degree during the printing operation. An impression of suchswelled surface is transferred to the surface being printed thusresulting in the production of an unsatisfactorily printed product.

The present invention provides for ink transfer media which haveexcellent ink transfer characteristics, defectfree surfaces andexcellent resistivity to the swelling action of practically all of thecommon ink solvents. Also, printing plates of the present invention,when heated to a temperature at which their surfaces become soft, i.e.,at their minimum surface softening temperature, lose their surfaceimprint and return to their original smooth surfaced form without losingtheir shape. As an additional ice feature, the printing plates of thisinvention perform in excellent fashion with half tone screens abovelines.

The ink transfer media of this invention are formed from cross-linkedthermoplastic resin compositions. Cross-linked thermoplastic resincompositions are not truly thermoplastic since they cannot be heated andremolded. The surfaces of cross-linked thermoplastic resin compositionscan be softened by heat, however, and in this condition readilydistorted. This surface distortion can be frozen in by simply coolingthe distorted material to a temperature below the softening pointthereof.

For purposes of this invention, thermoplastic resin compositions areconsidered to be cross-linked when at least about 85 percent by weightof a sample thereof is insoluble in boiling benzene after being immersedin boiling benzene for 24 hours.

The process by which the printing plates of the present invention areproduced is conducted by shaping and cross-linking a thermoplastic resincomposition, softening the surface of the shaped cross-linked articleand thereafter imprinting on the softened surface.

Formation of thermoplastic resin compositions into shaped articles canbe accomplished by any one of a number of convenient methods, as forexample, by extrusion, by casting, by compression molding, bycalendering and the like. The exact method used and the conditions underwhich such method is operated will, of course, depend upon the nature ofthe composition which is being shaped. The shape and size of the articlecan approximate that of the ultimate printing plate or the shapedarticle can be subsequently die cut, generally after being cross-linked,to the desired size. It is to be understood that the printing plate canbe of any desired shape and is not limited to a flat plate structure.

Cross-linking of the thermoplastic resin composition, in the form of ashaped article, is conveniently accomplished by admixing an organicperoxide catalyst with the thermoplastic resin composition prior to itsbeing shaped, forming the resultant composition into a shaped article,and heating the shaped article at a temperature sufficient to effectdecomposition of the organic peroxide and to effect cross-linking of themolecules of the thermoplastic resin composition. Cross-linking of theshaped article can be accomplished simultaneously with the shaping ofthe thermoplastic material or subsequent thereto.

The amount of organic peroxide used is sufficient to effect across-linking of the composition with which it has been admixed.Generally, this amount will vary from about 1 percent by weight to about6 percent by weight, and preferably from about 3 percent by weight toabout 4 percent by weight, based on the Weight of the thermoplasticresin. More than about 6 percent by weight of organic peroxide can beused but this does not materially affect the cross-linking reaction andis economically undesirable.

Once the organic peroxide is admixed with the thermoplastic resincomposition and the resultant composition formed into a shapedstructure, the shaped structure is heated at temperatures sufiicien'tlyhigh to decompose enough of the organic peroxide to effect cross-linkingof the thermoplastic resin composition. Ordinarily the shaped structuresare heated at a temperature of at least about C., and generally at atemperature of about 3 150 C. to about 200 C. and preferably at atemperature of about 175 C. to about 190 C. The actual time of theheating cycle will, of course, vary depending upon the organic peroxideused as well as the thermoplastic resin composition which is beingcross-linked.

Any organic peroxide which will preferably decompose at a temperatureabove but not below about 150 C. is suitable for effecting cross-linkingof the thermoplastic resin compositions.

Illustrative of suitable peroxides are the polymer hydroperoxides, suchas polyethylene hydroperoxide, and other such polymer hydroperoxides, asfor example are disclosed in U.S. Patent No. 2,911,398, issued November3, 1959 to Edwin J. Vandenberg; the perester peroxides, such as t-butylperacetate, t-butyl peroxyisobutyrate, di-t-butyl diperphthalate,t-butyl perbenzoate, di-t-butyl dipermethyl malonate, di-t-amyldipermethyl malonate, di-t-hexyl diperethyl succinate, di-t-hexyldipergluturate, di-t-amyl dipersuccinate and the like, for instance asare disclosed in U.S. Patent No. 2,763,635, issued September 18, 1956 toCharles M. Lucher et al., and as are disclosed in U.S. Patent No.2,698,863, issued January 4, 1955 to Frank H. Dickey; diacyl aromaticperoxides exemplary of which are the peroxides having the formula:

wherein R is an aryl radical, such as benzoyl peroxide,2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide and the like;diacyl aliphatic per-oxides, such as those having the formula:

wherein R is an alkyl group, as for example, acetyl penoxide, eaprylylperoxide, 'myristoyl peroxide, lauroyl peroxide and the like; dibasicacid peroxides, such as succinic acid peroxide; the ketone peroxides,such as methyl ethyl ketone peroxide, cyclohexanone peroxide and thelike; the aldehyde peroxides, such as hydroheptyl peroxide and the like;peroxides having the formula:

wherein R and R are alkyl groups, R is dialkyl methyl or trialkylmethyl; with the alkyl group in each case containing a maximum of 8carbon atoms and R is hydrogen or an alkyl group containing a maximum of8 carbon atoms such as 1,1-dim'ethyl-1-(isopropyl cyclohexyl)methylhydroperoxide, 1,l-dimethyl-l-(diisopropyl cyclohexyl)methylhydroperoxide and the like as are fur ther disclosed in U.S. Patent No.2,776,954 to Milton A. Taves; diQaralkyl) peroxides of the formula:

wherein R is aryl, R R R and R are hydrogen or alkyl groups of less than4 carbon atoms and R is aryl, such as dibenzyl peroxide,bis-(a-methylbenzyDperoxide, bi S-(zx,ot dimethy-lbenzyDperox-ide,blS-(oc propylbenzyl) peroxide, benzyl-(ot im-ethylbenzyDperoxide,benzy-l (0L- methyl-p-methylbenzyl)peroxide,benzyl-(a-methyl-p-isopropylbenzyl)peroxide and the like as are furtherdisclosed in U.S. Patent No. 2,826,570, issued March 11, 1958 toReginald W. Ivett; hydroperoxides, such as2,5-dimethylhexane-2,S-dihydroperoxide, p-menthane hyd-ropenox-ide,t-buity-lhydropetroxide, benzoin peroxide and the like; di-tertiaryalkyl peroxides such as di-t-butyl peroxide, 2,5-bis-(tertbutylperoxy)-2,5-dimethylhexane and the like.

Once the composition in the form of a shaped article is cross-linked,the surface of the shaped article is softened to a degree such that itcan be.imprinted on. This is accomplished, in general, by heating theshaped article to its minimum surface softening temperature. At thistemperature, the shaped article will retain its shape although itssurface will become soft enough to be imprinted on. The temperature atwhich each shaped structure is heated will depend upon the nature of thecomposition from which the shaped article was produced. As a generalrule, these temperatures are at least C., generally about 125 C. toabout 200 C. and preferably about C. to about 180 C. The time of theheating cycle will vary and depend upon the composition of the shapedstructure.

Imprinting on the softened surface of the shaped article is usuallyeffected by bringing the shaped article into contact with the surface ofa matrix board whose surface is to be imprinted onto the surface of theshaped article. The imprinting operation is usually conducted in a presswherein the matrix board and the shaped article are forced into intimatesurface contact with each other under sufiicient pressure so that thesurface of the matrix board is imprinted on the surface of the shapedarticle. Once the surface of the matrix board is imprinted on thesurface of the shaped article, appearing as a mirror image thereon, theshaped article is cooled to hardness, usually to room temperature, about23 C., removed from the press and then separated from the matrix board.

Illustrative of thermoplastic resins which can be used in accordancewith this invention are those formed by polymerizing one, or a mixtureof the following monomers: vinyl aryls such as styrene,o-methoxystyrene, pmethoxystyrene, m-methoxystyrene, o-nitrostyrene,m-nitrostyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene,p-phenylstyrene, o-phenylstyrene, m-phenylstyrene, vinylnaphthalene andthe like; vinyl and vinylidene halides such vinyl chloride, vinylidenechloride, vinylidene bromide and the like; vinyl esters such as vinylacetate, vinyl propionate, vinyl butyrate, vinyl chloroacetate, vinylchloropropionate, vinyl benzoate, vinyl chlorobenzoate and the like;acrylic and alpha-alkyl acrylic acids, their alkyl esters, their amidesand their nitriles such as acrylic acid, chloroacrylic acid, methacrylicacid, ethacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,n-otyl acrylate, Z-ethylhexyl acrylate, n-decyl acrylate, methylmethacrylate, butyl meithacrylate, methyl ethacrylate, ethylethacrylate, acrylamide, N-methyl acrylamide, N,N-dimethylacrylamide,methacrylamide, N-methyl methacrylamide, N,N-dimethyl methacrylamide,'acrylonitrile, chloroacrylonitrile, methacrylonitrile, ethacrylonitrileand the like; alkyl esters of maleic and fumaric acid such as dimethylmaleate, diethyl maleate and the like; vinyl alkyl esters and ketonessuch as vinyl methyl ether, vinyl ethylether, vinyl isobutyl ether,2-chloroethyl vinyl ether, methyl vinyl ketone, etheyl vinyl ketone,isobutyl vinyl ketone and the like; also vinyl pyridine, N-vinylcarbazole, N- vinyl pyrrolidine, ethyl methylene malonate; ethylene,propylene and the like. If desired, a mixture of thermoplastic resinscan be used. By using a mixture of resins of different densities thehardness of the end products can be varied as desired.

If desired, various additives can be added to the thermoplastic resinsas is well-known in the art. Exemplary of such additives are dyes,pigments such as titanium dioxide, stabilizers, lubricants, antioxidantssuch as 4,4'-thiobis-(3-methyl-tert-butylphenol), fillers such as carbonblack, talc, clay, wollastonite and the like.

The examples which follow are intended to illustrate the presentinvention, and are not intended to limit the scope thereof in anymanner.

Example I This example illustrates the excellent printing plates thatcan be produced according to the present invention. Compositions, whoseformulations are shown in the table below, were compounded and formedinto printing plates in a manner which will be described subsequently.The matrix board used in each of the examples contained screens of 65 to150 lines and contained various types, sizes and faces. The matrix boardwas a standard matrix board for type reproductions, supplied byWilliamson and Company of Caldwell, New Jersey.

ployed in a flat-bed, letter-press. excellent quality were obtained.

In order to demonstrate the necessity of cross-linking shaped articlesbefore imprinting thereon, compositions were formulated and thecompositions formed into blanks. The blanks were imprinted on withoutfirst being crosslinked.

Printed paper sheets of Parts by Weight Polyethylene, 0.95 Density, 6Melt Index Polyethylene, 0.914 Density, 1.25 Melt Index Ethylene-EthylAcrylate Copolymer, 10 Melt Index, 14 Weight Percent Combined Ethyl.Acrylate- Ethylene-Ethyl Acrylate Copolymer, 16 Melt Index, 20 WeightPercent Combined Ethyl Acrylate Ethylene-Ethyl Acrylate Copolymer, 0.1Melt Index, 12 Weight Percent Combined Ethyl Acrylate- ElectricallyNon-Conductive Carbon Black 1, 225

Electrically Conductive Carbon Black Bis (oi-a-dimethylbenzyl) peroxide4,4-Thio Bis-(3-methy1-6-t-butylphenol) 12 7. 5

Each composition noted in the table above, less the organic peroxide,was fluxed in a Banbury mixer at a batch temperature of from 110 C. to125 C. to a blend. The organic peroxide was then added to eachcomposition and .each composition was again fiuxed in the Banbury mixerat .a batch temperature of from 110 C. to 125 C. for 2 minutes. Eachcomposition was then removed from the Banbury mixer and given 5end-passes on a 16 inch by 24 'inch two-roll mill whose rolls surfacetemperaure was "110 C." Each sheeted composition was then cooled to roomtemperature, about 23 C. and cut into blanks havtemperature of 175 C.Each blank was allowed to remain in the heated press under a pressure of300 p.s.i. absolute to 600 p.s.i. absolute for 10 minutes. Each blankwas then cooled to room temperature, about 23 C. and removed from themold.

Each cross-link blank was placed onto the surface of a matrix board,having lettering imprinted thereon, which was approximately the samesize as the cross-linked blank.

The cross-linked blank, resting on the surface of the matrix board, washeated at 175 C. for 5 minutes with the result that the surface of theblank softened. At this point the "cross-linked blank and the matrixboard were placed in a cold press and pressed into intimate surfacecontact under pressure. The blank was then allowed to cool to roomtemperature, about 23 C. while still in contact, under 'pressure, withthe matrix board in the press, removed from the press along with thematrix board and then separated from the matrix board.

All of the printing plates so produced had imprinted on their surfaces aperfect mirror image of the lettering of the .matrix board. Theimprinted surface of each printing ,plate was free from any surfacedefects. 1

Printing plates formed from Composition 4 were em- Each compositionnoted in the table above, less the organic peroxide, was fluxed in aBanbury mixer at a batch temperature of from C. to C. to a blend. Theorganic penoxide was then added to each composition and each compositionwas again fluxed in the Banbury mixer at a batch temperature of from 110C. to 125 C. for 2 minutes. Each composition was then removed from theBanbury mixer and given 5 end-passes on a 16 inch by 24 inch two-rollmill whose rolls surface temperature was 110 C. Each sheet-edcomposition was then cooled to room temperature, about 23 C. andcut intofour inch square blanks; A blank, corresponding in size to that of amatrix board, which had lettering thereon and which was used to imprintthat lettering onto the blank, was placed in surf-ace contact with thematrix board. I I

Each blank, in intimate surface contact with the matrix board underpressure was heated at C. for 10 minutes. The blank was then allowed tocool to room temperature, about 23 C., then separated from the matrixboard.

All of the printing plates so produced had undesirable surface fissureswhich rendered them useless for obtaining there-from acceptable printedmaterial such as printed paper sheets.

Example 11 This example illustrates the excellent resistance to theswelling effects of the common ink solvents possessed by printing platesof the present invention as compared to rubber printing plates.

Small samples from printing plates formed from compositions identifiedas 1, 2 and 7 in Example I, and produced according to the proceduredescribed in Example I were submerged in various solvents for 24 hoursat 23 C. After 24 hours each sample was removed from the solvent and itspercent volume change determined using a micrometer. Samples fromprinting plates formed from synthetic rubber (polymer of acrylonitrileand 1,3-butadiene), and from natural rubber (caoutchouc) were alsoimmersed in various solvents for 24 hours at 23 C., removed therefromand their percent volume change determined. The

rubber printing plates were supplied by Moss Type Corporation.

Type of solvents used and the percent volume change of each sample arenot-ed in the table which follows:

As shown by the above noted table, printing plates formed in accordancewith the present invention have a significantly greater resistance tothe swelling action of commonly used ink solvents than do printingplates formed from natural or synthetic rubber.

Example III This example also illustrates that excellent printing platescan be produced in accordance with the present invention.

Compositions, Whose formulations are shown in the Printing plates formedfrom these compositions were employed in a fiat-bed, letter-press.Printed paper sheets of excellent quality were obtained.

Example V Compositions, whose formulations are shown in the table below,were compounded and formed into printing plates in a manner identical tothat described in Example I.

Parts by Weight 15 Polyethylene 0.914 density, 1.2 Melt Index. 50 50 5O50 Electrically non-conductive carbon black. 12. 5 37. 5Bis-(a,a-dimcthylbenzyl) peroxide 1. 5 1. 5 1. 5 1. 54,4-Thiobis(3-methyl-G-t-butylphenol) 0.05 0.05 0.05 0.05

Printing plates formed from these compositions were employed in afiexographic printing press. Printed paper sheets of excellent qualitywere obtained.

Example VI Compositions, Whose formulations are shown in the tablebelow, were compounded and formed into fiexographic printing plates in amanner identical to that described in Example I.

Parts by Weight Ethylene-Ethyl Aerylate Copolymer, 1O Melt Index, 14

Weight Percent Combined Ethyl Acrylate Ethylene-Ethyl AcrylateCopolymer, 15.7 Melt Index, 19

Weight Percent Combined Ethyl Acrylate Ethylene-Ethyl AcrylateCopolymer, 18.8 Melt Index.

26.1 Weight Percent Combined Ethyl Acrylate Ethylene-Ethyl AcrylateCopolymer, 26.4. Melt Index, 16

Weight Percent Combined Ethyl Aerylate Ethylene-Ethyl AcrylatcCopolymer, 0.1 Melt Index, 5

Weight Percent Combined Ethyl Acrylate Electrically Conductive CarbonBlack Electrically Non-Conductive Carbon BlackBis-(a,a-dimethylbenzyl)peroxide table below, were compounded and formedinto printing plates in a manner identical to that described in ExampleI.

Parts by Weight Polyethylene, 0.95 density, 6 Melt Index 50Polyethylene, 0.95 density, 4 Melt Index. 50 Electrically non-conductivecarbon blaclr-. 5O 50 2,513 is-(t-butylperoxy)-2,5-dimethyl hexane 1. 5Bis-(a,a-dimethylbenzyl) peroxide 1. 5 Polymerized trimethyldihydroquinolinc 0.05 4,4-Thio bis-(3-1nethyl-t-5-butylphenol) 0.05

Printing plates formed from both compositions were employed in aflat-bed, letter-press. Printed paper sheets of excellent quality wereobtained.

Example IV Compositions, whose formulations are shown in the tablebelow, were compounded and formed into printing plates in a manneridentical to that described in Example I.

Parts by Weight Polyethylene, 0.914 density, 1.2 Melt Index 50 50 50Electrically non-conductive carbon black 50 Bis-(a,a-dimethylbenzyl)peroxlde 1, 5 1.5 1. 5 4,4-Thio bis-(3-methyl-6-t-butylphenol) 0. 05 0.05 0.05

All of the printing plates so produced had imprinted on their surfaces aperfect mirror image of the lettering of the matrix board. The imprintedsurface of each printing plate was free from any surface defects.

Example VII A composition Whose formulation is shown below, wascompounded and formed into printing plates in a manner identical to thatdescribed in Example 1.

Parts by weight 23 Polyethylene, 0.95 density, 6 Melt Index 1,225Electrically non-conductive carbon black 1,225 Bis-(a,a-dimethylbenzyl)peroxide 73.5 4,4'-Thio-bis-(3-methyl-6-tt-butylphenol) 12 The printingplates formed were heated to a temperature of C. with the result thateach printing plate returned to its blank surfaced form that itpossessed prior to being imprinted on, Without losing its shape. Theseblanks were then used to prepare new printing plates.

It is to be noted that all patents noted in this application areincorporated herein by reference.

What is claimed is:

1. Process for the production of a printing plate which comprises insequence the steps of heating a cross-linked shaped article formed froma thermoplastic resin composition having an organic peroxide content offrom about 1% to about 6%, to a temperature such that the surface ofsaid article is softened, pressing a matrix board having an imprint onits surface into intimate contact with the softened surface of saidcross-linked shaped article whereby the surface of said matrix board isimprinted on the surface of said cross-linked shaped article, appearingas a mirror image thereon, cooling said cross-linked shaped article toabout room temperature while maintaining said cross-linked shapedarticle in contact with said matrix board and thereafter separating saidcrosslinked shaped article from said matrix board.

2. Process for the production of a printing plate which comprises insequence the steps of forming a thermoplastic resin composition havingan organic peroxide content of from about 1% to about 6%, into a shapedarticle, cross-linking said shaped article, heating said cross-linkedshaped article to a temperature such that the surface of said article issoftened, pressing a matrix board having an imprint on its surface intointimate contact with the softened surface of said cross-linked shapedarticle whereby the surface of said matrix board is imprinted on thesurface of said cross-linked shaped article, appearing as a mirror imagethereon, cooling said cross-linked shaped article to about roomtemperature while maintaining said cross-linked shaped article incontact with said matrix board and thereafter separating saidcrosslinked shaped article from said matrix board.

3. Process for the production of a printing plate which comprises insequence the steps of admixing a thermoplastic resin with about 1% toabout 6% of an organic peroxide, forming the resultant compositioninto ashaped article, heating said article to effect a cross-linking thereof,heating the cross-linked shaped article to a temperature such that thesurface of said article is softened, pressing a matrix board having animprint on its surface into intimate contact with the softened surfaceof said crosslinked shaped article whereby the surface of said matrixboard is imprinted on the surface of said cross-linked shaped article,appearing as a mirror image thereon, cooling said cross-linked shapedarticle to about room temperature while maintaining said cross-linkedshaped article in contact with said matrix board and thereafterseparating said cross-linked shaped article from said matrix board.

4. Process as defined in claim 3 wherein the thermoplastic resin ispolyethylene.

5. Process as defined in claim 3 wherein the thermoplastic resin is acopolymer of ethylene and ethyl acrylate.

6. Process as defined in claim 3 wherein the organic peroxide isbis(a,a-dimethylbenzyl)peroxide.

7. Process as defined in claim 3 wherein the organic peroxide is2,5-bis-(t-butylperoxy)-2,5-dimethyl hexane.

8. Process for the production of a printing plate which article incontact with said matrix board and thereafter separating saidcross-linked shaped article from said matrix board.

9. Process as defined in claim 8 wherein said crosslinked shaped articleis heated at a temperature of about 125 C. to about 200 C.

10. Process as defined in claim 8 wherein the filler is carbon black.

comprises in sequence the steps of admixing a thermoplastic resin andfrom about 1% to about 6% of an organic peroxide and a filler, formingthe resultant composition into a shaped article, heating said shapedarticle at a temperature of about C. to about 200 C.

11. Process for the production of a printing plate which comprises insequence the steps of admixing a thermoplastic resin, and from about 1%to about 6% of an organic peroxide, and a filler, forming the resultantcomposition into a shaped article, heating said shaped article at atemperature of about C. to about 190 C. to effect a cross-linkingthereof, heating said cross-linked shaped article at a temperature ofabout 150 C. to about 180 C. to elfect a softening of the surfacethereof, pressing a matrix board having an imprint on its surface intointimate contact with the softened surface of said crosslinked shapedarticle whereby the surface of said matrix board is imprinted on thesurface of said cross-linked shaped article, appearing as a mirror imagethereon, cooling said cross-linked shaped article to about roomtemperature while maintaining said cross-linked shaped article incontact with said matrix board and thereafter separating saidcross-linked shaped article from said matrix board.

References Cited by the Examiner UNITED STATES PATENTS 2,510,999 6/ 1950Oldofredi. 2,578,209 12/1951 Schwarz 264293 2,628,214 2/195 3 Pinkney eta1. 2,826,570 3/ 1958 Ivett 260-949 2,910,456 10/1959 Koch de Gooreynd.2,912,418 11/1959 Johnson et al. 3,013,305 12/ 1961 Koch de Gooreynd.3,049,517 8/ 1962 Caton.

ROBERT F. WHITE, Primary Examiner.

M. R. DOWLING, Assistant Examiner.

1. PROCESS FOR THE PRODUCTION OF A PRINTING PLATE WHICH COMPRISES INSEQUENCE THE STEPS OF HEATING A CROSS-LINKED SHAPED ARTICLE FORMED FROMA THERMOPLASTIC RESIN COMPOSITION HAVING AN ORGANIC PEROXIDE CONTENT OFFROM ABOUT 1% TO ABOUT 6%, TO A TEMPEREATURE SUCH THAT THE SURFACE OFSAID ARTICLE IS SOFTENED, PRESSING A MATRIX BOARD HAVING AN IMPRINT ONITS SURFACE INTO INTIMATE CONTACT WITH THE SOFTENED SURFACE OF SAIDCROSS-LILNKED SHAPED ARTICLE WHEREBY THE SURFACE OF SAID MATRIX BOARD ISIMPRINTED ON THE SURFACE OF SAID CROSS-LINKED SHAPED ARTICLE, APPEARINGAS A MIRROR IMAGE THEREON, COOLING SAID CROSS-LINKED SHAPED ARTICLE TOABOUT ROOM TEMPERATURE WHILE MAINTAINING SAID CROSS-LIKED SHAPED ARTICLEIN CONTACT WITH SAID MATRIX BOARD AND THEREAFTER SEPARATING SAIDCROSSLINKED SHAPED ARTICLE FROM SAID MATRIX BOARD.